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Science at key stage 3    (Year 9)

Unit 9F: Patterns of reactivity
Section 5: a. Can metals displace each other?

QCA

Objectives
Children should learn:
  • that a metal will displace a less reactive metal from a solution of one of its salts
  • to construct a table to show patterns clearly
  • to identify patterns in observations
  • to use a model to explain results

Activities

Outcomes
Children:
  • Provide pupils with small samples of metals, eg magnesium, iron, copper, zinc, and solutions of metal salts, eg zinc sulphate, iron (II) sulphate, copper sulphate, silver nitrate. Ask pupils to plan tests of combinations of metal and metal salt to find out if there is a reaction, recording their results in a table. Ask pupils to find a pattern in their results and, if possible, to reorder their table to show the results more clearly. Discuss the results with the pupils and use an analogy or model to explain the displacement of the less reactive metal by the more reactive one. Ask pupils to predict whether other reactions will occur.
  • Show using an analogy, eg 'pull' of metal on the sulphate, and word or symbol equations that whether there is a reaction or not depends on the metal and the metal in the salt, not on the acid from which the salt was derived.
  • If appropriate, link to work pupils have done on the voltages of simple cells.
  • identify where reactions occur and where they do not
  • relate their results to the position of the metal in the reactivity series
  • articulate the pattern, eg it's the metal that's important; a metal high in the reactivity series will push out one lower down, but a lower one won't push out a higher one
  • use an analogy or model to explain the results, eg the zinc has a stronger pull on the sulphate than the copper does

Points to note
  • Using very small quantities in a dimple tile works well. In some cases, eg if magnesium is added to copper sulphate solution, the reaction may be between the water and the metal rather than between the salt and the metal.
  • This activity provides an opportunity to use ICT to reorder tables of results.
  • This work could be extended to heating metals, eg copper, zinc, with metal oxides to determine whether there is a reaction. Some mixtures may be dangerous.
  • Although analogies, eg 'pull' of metal, are not strictly correct, they may be helpful to pupils in establishing principles about displacement.
  • Extension: pupils could be asked to write the symbols and formulae for reactants and products, and from these write symbol equations.

    • Safety

    • 0.4 mol dm-3 or 0.1 mol dm-3 solutions of salts can be used. Eye protection should be worn
    • appropriate risk assessments should be followed before practical work begins

Sections in this unit

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This unit is divided into sections. Each section contains a sequence of activities with related objectives and outcomes. You can view this unit by moving through the sections or print/download the whole unit.
1. Why do metals tarnish?
2. How do metals react with water?
3. Is the order of reactivity of metals with water the same as that with acids?
4. Can we make predictions about the reactions of metals with oxygen?
5. a. Can metals displace each other?
6. b. Can metals displace each other?
7. Checking progress
8. How does the activity series relate to uses and sources of metals?
9. How can we find out more about the reaction of metals with acids?
10. Reviewing work